Part marking exists to answer a question later: what is this, where did it come from, and which batch was it in. That means the mark has to survive everything that happens to the part between marking and reading, and the most common failure is a mark that is applied before a finishing process that removes it.
The methods
Laser marking changes or removes the surface and is the industrial default: fast, permanent, no consumables and easily serialised. Dot peen indents the surface mechanically and is very robust on rough or curved surfaces. Electrochemical etching marks stainless and other conductive metals without heat, which matters on stress sensitive parts. Ink jet and label printing are cheap and impermanent by comparison.
Choosing on what happens next
A mark applied before blasting, anodising, plating or painting may be reduced or removed. A shallow laser mark on aluminium can disappear under a blast; an ink mark will not survive solvent cleaning. Decide the mark's position in the process sequence at the same time as the method, and test the whole chain rather than the mark alone.
Traceability and machine readability
Where the mark carries a serial number or a data matrix code, it has to be readable by machine after everything the part goes through, and readability is a measurable grade rather than a yes or no. Contrast, cell size, quiet zone and surface finish all affect it. A code that scans off the marker and fails after passivation is a common and avoidable failure.
Regulatory and stress considerations
Some sectors mandate unique device or part identification with a defined format, so the marking method is a compliance question rather than a preference. On fatigue critical parts, any mark that indents or heats the surface is a stress raiser, which is why electrochemical etching and low stress marking methods exist and why marking position is a design decision on such parts.
Questions people ask about part marking
Which part marking method is most permanent?
Laser and dot peen marks are permanent in the material itself. Ink and labels are not, and electrochemical etching sits between the two in depth.
Will my mark survive finishing?
Not necessarily. Blasting, anodising, plating and painting can all reduce or remove a shallow mark. Decide the marking position in the sequence, and test the whole chain.
What affects whether a code scans?
Contrast, cell size, quiet zone and surface finish. Readability is graded rather than binary, and it can degrade after downstream processing.
Can marking weaken a part?
Any method that indents or heats the surface creates a stress raiser. On fatigue critical parts, use a low stress method and choose the position deliberately.